Refactor gold to enable support for MIPS-64 relocation format.

Refactor gold to enable support for MIPS-64 relocation format.

For MIPS-64, the r_info field in the relocation format is
replaced by several individual fields, including r_sym and
r_type. To enable support for this format, I've refactored
target-independent code to remove almost all uses of the r_info
field. (I've left alone a couple of routines used only for
incremental linking, which I can update if/when the MIPS target
adds support for incremental linking.)

For routines that are already templated on a Classify_reloc class
(namely, gc_process_relocs, relocate_section, and
relocate_relocs), I've extended the Classify_reloc interface to
include sh_type (which no longer needs to be a separate template
parameter) as well as get_r_sym() and get_r_type() methods for
extracting the r_sym and r_type fields. For
scan_relocatable_relocs, I've extended the
Default_scan_relocatable_relocs class by converting it to a class
template with Classify_reloc as a template parameter. For the
remaining routines that need to access r_sym, I've added a
virtual Target::get_r_sym() method with an override for the MIPS
target.

In elfcpp, I've added Mips64_rel, etc., accessor classes and
corresponding internal data structures. The MIPS target uses
these new classes within its own Mips_classify_reloc class.
The Mips64_ accessor classes also expose the r_ssym, r_type2,
and r_type3 fields from the relocation.

These changes should be functionally the same for all but the
MIPS target.

elfcpp/
	* elfcpp.h (Mips64_rel, Mips64_rel_write): New classes.
	(Mips64_rela, Mips64_rela_write): New classes.
	* elfcpp_internal.h (Mips64_rel_data, Mips64_rela_data): New structs.

gold/
	* gc.h (get_embedded_addend_size): Remove sh_type parameter.
	(gc_process_relocs): Remove sh_type template parameter.
	Use Classify_reloc to access r_sym, r_type, and r_addend fields.
	* object.h (Sized_relobj_file::split_stack_adjust): Add target
	parameter.
	(Sized_relobj_file::split_stack_adjust_reltype): Likewise.
	* reloc-types.h (Reloc_types::copy_reloc_addend): (SHT_REL and SHT_RELA
	specializations) Remove.
	* reloc.cc (Emit_relocs_strategy): Rename and move to target-reloc.h.
	(Sized_relobj_file::emit_relocs_scan): Call Target::emit_relocs_scan().
	(Sized_relobj_file::emit_relocs_scan_reltype): Remove.
	(Sized_relobj_file::split_stack_adjust): Add target parameter.
	Adjust all callers.
	(Sized_relobj_file::split_stack_adjust_reltype): Likewise. Call
	Target::get_r_sym() to get r_sym field from relocations.
	(Track_relocs::next_symndx): Call Target::get_r_sym().
	* target-reloc.h (scan_relocs): Remove sh_type template parameter;
	add Classify_reloc template parameter.  Use for accessing r_sym and
	r_type.
	(relocate_section): Likewise.
	(Default_classify_reloc): New class (renamed and moved from reloc.cc).
	(Default_scan_relocatable_relocs): Remove sh_type template parameter.
	(Default_scan_relocatable_relocs::Reltype): New typedef.
	(Default_scan_relocatable_relocs::reloc_size): New const.
	(Default_scan_relocatable_relocs::sh_type): New const.
	(Default_scan_relocatable_relocs::get_r_sym): New method.
	(Default_scan_relocatable_relocs::get_r_type): New method.
	(Default_emit_relocs_strategy): New class.
	(scan_relocatable_relocs): Replace sh_type template parameter with
	Scan_relocatable_relocs class.  Use it to access r_sym and r_type
	fields.
	(relocate_relocs): Replace sh_type template parameter with
	Classify_reloc class.  Use it to access r_sym and r_type fields.
	* target.h (Target::is_call_to_non_split): Replace r_type parameter
	with pointer to relocation. Adjust all callers.
	(Target::do_is_call_to_non_split): Likewise.
	(Target::emit_relocs_scan): New virtual method.
	(Sized_target::get_r_sym): New virtual method.
	* target.cc (Target::do_is_call_to_non_split): Replace r_type parameter
	with pointer to relocation.

	* aarch64.cc (Target_aarch64::emit_relocs_scan): New method.
	(Target_aarch64::Relocatable_size_for_reloc): Remove.
	(Target_aarch64::gc_process_relocs): Use Default_classify_reloc.
	(Target_aarch64::scan_relocs): Likewise.
	(Target_aarch64::relocate_section): Likewise.
	(Target_aarch64::Relocatable_size_for_reloc::get_size_for_reloc):
	Remove.
	(Target_aarch64::scan_relocatable_relocs): Use Default_classify_reloc.
	(Target_aarch64::relocate_relocs): Use Default_classify_reloc.
	* arm.cc (Target_arm::Arm_scan_relocatable_relocs): Remove sh_type
	template parameter.
	(Target_arm::emit_relocs_scan): New method.
	(Target_arm::Relocatable_size_for_reloc): Replace with...
	(Target_arm::Classify_reloc): ...this.
	(Target_arm::gc_process_relocs): Use Classify_reloc.
	(Target_arm::scan_relocs): Likewise.
	(Target_arm::relocate_section): Likewise.
	(Target_arm::scan_relocatable_relocs): Likewise.
	(Target_arm::relocate_relocs): Likewise.
	* i386.cc (Target_i386::emit_relocs_scan): New method.
	(Target_i386::Relocatable_size_for_reloc): Replace with...
	(Target_i386::Classify_reloc): ...this.
	(Target_i386::gc_process_relocs): Use Classify_reloc.
	(Target_i386::scan_relocs): Likewise.
	(Target_i386::relocate_section): Likewise.
	(Target_i386::scan_relocatable_relocs): Likewise.
	(Target_i386::relocate_relocs): Likewise.
	* mips.cc (Mips_scan_relocatable_relocs): Remove sh_type template
	parameter.
	(Mips_reloc_types): New class template.
	(Mips_classify_reloc): New class template.
	(Target_mips::Reltype): New typedef.
	(Target_mips::Relatype): New typedef.
	(Target_mips::emit_relocs_scan): New method.
	(Target_mips::get_r_sym): New method.
	(Target_mips::Relocatable_size_for_reloc): Replace with
	Mips_classify_reloc.
	(Target_mips::copy_reloc): Use Mips_classify_reloc.
	(Target_mips::gc_process_relocs): Likewise.
	(Target_mips::scan_relocs): Likewise.
	(Target_mips::relocate_section): Likewise.
	(Target_mips::scan_relocatable_relocs): Likewise.
	(Target_mips::relocate_relocs): Likewise.
	(mips_get_size_for_reloc): New function, factored out from
	Relocatable_size_for_reloc::get_size_for_reloc.
	(Target_mips::Scan::local): Use Mips_classify_reloc.
	(Target_mips::Scan::global): Likewise.
	(Target_mips::Relocate::relocate): Likewise.
	* powerpc.cc (Target_powerpc::emit_relocs_scan): New method.
	(Target_powerpc::Relocatable_size_for_reloc): Remove.
	(Target_powerpc::gc_process_relocs): Use Default_classify_reloc.
	(Target_powerpc::scan_relocs): Likewise.
	(Target_powerpc::relocate_section): Likewise.
	(Powerpc_scan_relocatable_reloc): Convert to class template.
	(Powerpc_scan_relocatable_reloc::Reltype): New typedef.
	(Powerpc_scan_relocatable_reloc::reloc_size): New const.
	(Powerpc_scan_relocatable_reloc::sh_type): New const.
	(Powerpc_scan_relocatable_reloc::get_r_sym): New method.
	(Powerpc_scan_relocatable_reloc::get_r_type): New method.
	(Target_powerpc::scan_relocatable_relocs): Use
	Powerpc_scan_relocatable_reloc.
	(Target_powerpc::relocate_relocs): Use Default_classify_reloc.
	* s390.cc (Target_s390::emit_relocs_scan): New method.
	(Target_s390::Relocatable_size_for_reloc): Remove.
	(Target_s390::gc_process_relocs): Use Default_classify_reloc.
	(Target_s390::scan_relocs): Likewise.
	(Target_s390::relocate_section): Likewise.
	(Target_s390::Relocatable_size_for_reloc::get_size_for_reloc):
	Remove.
	(Target_s390::scan_relocatable_relocs): Use Default_classify_reloc.
	(Target_s390::relocate_relocs): Use Default_classify_reloc.
	* sparc.cc (Target_sparc::emit_relocs_scan): New method.
	(Target_sparc::Relocatable_size_for_reloc): Remove.
	(Target_sparc::gc_process_relocs): Use Default_classify_reloc.
	(Target_sparc::scan_relocs): Likewise.
	(Target_sparc::relocate_section): Likewise.
	(Target_sparc::Relocatable_size_for_reloc::get_size_for_reloc):
	Remove.
	(Target_sparc::scan_relocatable_relocs): Use Default_classify_reloc.
	(Target_sparc::relocate_relocs): Use Default_classify_reloc.
	* tilegx.cc (Target_tilegx::emit_relocs_scan): New method.
	(Target_tilegx::Relocatable_size_for_reloc): Remove.
	(Target_tilegx::gc_process_relocs): Use Default_classify_reloc.
	(Target_tilegx::scan_relocs): Likewise.
	(Target_tilegx::relocate_section): Likewise.
	(Target_tilegx::Relocatable_size_for_reloc::get_size_for_reloc):
	Remove.
	(Target_tilegx::scan_relocatable_relocs): Use Default_classify_reloc.
	(Target_tilegx::relocate_relocs): Use Default_classify_reloc.
	* x86_64.cc (Target_x86_64::emit_relocs_scan): New method.
	(Target_x86_64::Relocatable_size_for_reloc): Remove.
	(Target_x86_64::gc_process_relocs): Use Default_classify_reloc.
	(Target_x86_64::scan_relocs): Likewise.
	(Target_x86_64::relocate_section): Likewise.
	(Target_x86_64::Relocatable_size_for_reloc::get_size_for_reloc):
	Remove.
	(Target_x86_64::scan_relocatable_relocs): Use Default_classify_reloc.
	(Target_x86_64::relocate_relocs): Use Default_classify_reloc.

	* testsuite/testfile.cc (Target_test::emit_relocs_scan): New method.